FBI stands for “Federal Bureau of Investigation” and CIA for “Central Intelligence Agency.” Both of them are part of the US Department of Justice and they work together and share information. The main difference between the two can be illustrated in their names: the FBI investigates crimes and the CIA gathers intelligence. The FBI investigates crimes committed in the USand collects information related to security in the US(although their work may take them abroad too). The CIA is an international intelligence agency that provides intelligence (information concerning an enemy) about terror drug smuggling etc. from all over the world to the USgovernment. There are other differences too: the CIA does a lot of research and background checks before something happens while the FBI moves into action after an event has happened. And the FBI is more visible while the CIA is more secretive — you may have seen FBI agents (or at least photos of them) but when was the last time you’ve seen a CIA detective?